In a telecommunications system, the devices involved with a telecommunications call or connection are referred to as the originating device and the terminating device, respectively. The originating device is where the user initiates the communication, and the terminating device is the device used by the person called by the originating device. To initiate a telecommunications communication, the user typically enters an identifying number of the person called into the originating device.
If the telecommunications call is made on a traditional telecommunication network, the originating device will accept the entry of the identifying number and perform a call setup procedure that establishes, among other things, a switched connection between the originating device and the terminating device. On a traditional telecommunications network, this switched connection will maintain an open connection between the originating and terminating device during the telecommunication call.
In Internet Protocol (IP) networks, the communication process is very different from a traditional telecommunication system. In an IP network, there is no open switched connection established between the originating and terminating devices. The information being transmitted between the originating and terminating devices is broken into packets of data, each of which is transmitted independently over the network to the terminating devices. Upon receipt by the terminating devices, the packets are reassembled into a coherent stream of voice or data.
A wireless communication system is very different from a traditional land-based communication system. For instance, a cellular system operates on a grid of cellular sites where two-way radio transmissions support the communication. Wireless networks can operate using different communication protocols, and hybrid systems are available which use packet-based communications on a wireless network.
In order for different types of telecommunication networks to communicate, there is a need for a consistent scheme for routing of data across the system boundaries, especially on interface boundaries between a wireless network and a packet-based communication system.